JP3490943B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire capable of improving wandering performance.

[0002]

2. Description of the Related Art Pneumatic tires, especially radial tires for heavy loads, which are filled with a high internal pressure and whose tread portion is reinforced by a tough belt layer, have high rigidity at the shoulder portion, and therefore, when traveling on a rutted road surface, for example. The so-called wandering phenomenon in which the handle is taken in tends to occur. In order to suppress such a wandering phenomenon, that is, to improve the wandering performance, it is known that it is effective to reduce the rigidity of the shoulder portion and shift the camber thrust to the positive side. Conventionally,
As shown in FIG. 8 (A), means for forming a narrow groove a extending in the circumferential direction in the vicinity of the tread edge TE, and as shown in FIG. 8 (B), the contour shape of the shoulder portion b in the meridional section is defined. A means for adopting a so-called round shoulder having a small arc b1, and a means for providing a large number of sipes c extending in the tire axial direction on the tread edge TE as shown in FIG.

[0003]

However, as shown in FIG.
As shown in (A) and (C), the thin groove a and the sipe c are formed in the tread edge TE.
As a result, abnormal wear such as heel & toe wear and shoulder drop wear is likely to occur at the shoulder portion, and damage such as rubber breakage is also likely to occur. Further, as shown in FIG. 8 (B), when the tread edge is round shouldered, the running performance tends to be impaired such that the ground contact width is greatly reduced.

The inventors of the present invention have conducted various studies in order to improve wandering performance while maintaining wear resistance in a pneumatic tire having shoulder blocks arranged on the tread surface along the tread edge. As a result, improving the shape of the buttress surface of the shoulder block, that is, the buttress contour line in the cylindrical cross section of the radius r centering on the tire axis of the buttress surface has an arcuate curve that is convex outward in the tire axial direction. None, and on the basis of providing a curved surface portion made of a curved surface whose radius of curvature of the arc-shaped curve becomes large as the radius r is reduced, the rigidity of the tread edge is relaxed without extremely reducing the rigidity of the shoulder block. I found that it can be realized.

As described above, the present invention is a pneumatic tire capable of effectively improving wandering performance without causing problems such as uneven wear, rubber chipping, or a large reduction in ground contact width, particularly preferably for heavy loads. Intended to provide tires.

[0006]

In order to achieve the above object, the invention according to claim 1 of the present invention provides a longitudinal main groove extending continuously in the tire circumferential direction near the tread edge, and the longitudinal main groove. A lateral tire that is continuous between a groove and the tread edge, and a pneumatic tire in which a shoulder block defined by the tread edge forms a row of blocks arranged in the tire circumferential direction, the tread end of the shoulder block being a tire. buttress surface contiguous to the edge, the buttress contour of cylindrical cross-section of radius r centered at the tire axis, an arc shape curve that is convex toward the outer side in the tire axial direction, yet with to reduce the radius r the sheet with comprises a curved surface portion radius of curvature of the arcuate curve is a curved surface that approaches the atmospheric next straight <br/> line, the curved surface portion, the radius of curvature of the arcuate curve in the tread edge It is characterized in that a 1.5 to 4.5 times the tire circumferential direction length L of the holder block.

Such a pneumatic tire is provided with a curved surface portion on the buttress surface of the shoulder block,
Rigidity relaxation on the tread edge side of the block can be realized without significantly reducing its rigidity, and wandering performance is effectively improved without causing problems such as uneven wear, lack of rubber or a large reduction in ground contact width. sell. That is, for example, when the buttress surface of the shoulder block collides with the slope of the rut road, the rigidity of the shoulder block is optimized, so that the camber thrust in the direction of climbing this slope is generated on the tire, and the rudder gets on and off smoothly. It can be carried out.

The curved surface portion can be constituted by a curved surface in which the radius of curvature of the arc-shaped curve gradually increases as the radius r is reduced. Further, preferably, it is particularly effective to prevent wandering that the curved surface portion is formed in the tire radial inner area from the tread edge.
Further, a flat surface portion in which the buttress contour line is a straight line may be formed inside the curved surface portion in the tire radial direction. This allows the rigidity of the shoulder block to be further optimized.

In the shoulder block, the curved surface portion may be formed on the tread edge through a small-width inclined surface portion that extends inward in the tire radial direction toward the tire axial outer side. In this case, the camber thrust is made larger by the inclined surface portion, and the effect of improving the wandering performance is further enhanced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings by taking a radial heavy tire (hereinafter sometimes simply referred to as "tire") as an example. FIG. 1 shows a developed view of the tread surface 2, which comprises a vertical main groove 3 extending continuously in the tire circumferential direction and a lateral groove 4 intersecting with the vertical main groove 3. There is.

A plurality of vertical main grooves 3 are arranged in this example. That is, the vertical main grooves 3 are, for example, a pair of vertical main grooves 3a, 3a arranged on both sides of the tire equator C, and a pair of outer vertical grooves arranged on the respective outer sides in the tire axial direction, close to the tread edge E. The main groove 3b, 3b, and in this example, the tread surface 2
A total of four are formed. Each of the vertical main grooves 3 is formed in a zigzag shape in the tire circumferential direction and continuously formed in the tire circumferential direction, but may be changed in various shapes such as a linear shape or a sinusoidal shape.

Further, in this example, the lateral groove 4 is a first lateral groove 4a connecting the inner longitudinal main grooves 3a, 3a, and extends from the inner longitudinal main groove 3a to the outside in the axial direction of the tire and the outer longitudinal main groove 3a. Groove 3
The second lateral groove 4 which terminates intermittently without communicating with b
b, a third lateral groove 4c extending inward in the tire axial direction from the outer longitudinal main groove 3b and terminating intermittently without communicating with the inner longitudinal main groove 3a, and a tire shaft from the outer longitudinal main groove 3b. The fourth extending outward in the direction and opening at the tread edge E
One including the lateral groove 4d is exemplified. The second and third
In this example, the lateral grooves 4b and 4c are shown as being communicated with each other by the narrow groove 16.

The groove width, groove depth, etc. of each of the vertical main grooves 3 and each of the horizontal grooves 4 can be variously set as required. For example, the groove width of the vertical main groove 3 is 2.0% of the tread ground contact width TW.
The above is more preferably 2.5% or more, and in the case of a heavy duty tire as in this example, it is preferable that the tire is continuously formed with a width of at least 5 mm or more. Further, it is desirable that the groove width of each lateral groove 4 is, for example, 1.5% or more of the tread ground contact width TW. Further, the groove depth of the vertical main groove 3 is, for example, 5 to 12% of the tread ground contact width TW, and the groove depth of the lateral groove 4 is
For example, it is desirable that the tread contact width TW is 2 to 12%.

The tread ground contact width TW is a tire axial distance between the outermost tread edges E, E when the tire is assembled on a regular rim and a regular internal pressure and a regular load are applied to contact the plane. As specified. At this time, "regular rim"
Is a rim that is defined for each tire in the standard system including the standard on which the tire is based.
Standard rim for TMA, "Design Rim" for TRA,
Or if it is ETRTO, it will be "Measuring Rim". Also,
"Regular internal pressure" is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, and for TRA, the table "T
IRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE
Maximum value described in "S", and if it is ETRTO, "INFLATION PRESS
In addition, "regular load" is the load that each standard defines for each tire in the standard system including the standard on which the tire is based, and if JATMA is the maximum load capacity, TRA For example, "TIRE LOAD LIMITS AT VARIOUS
Maximum value stated in "COLD INFLATION PRESSURES", and "LOAD CAPACITY" for ETRTO.

The tire of this embodiment has a tread surface 2
A shoulder block 6 defined by the outer vertical main groove 3b, a fourth lateral groove 4d continuous between the outer vertical main groove 3b and the tread edge E, and the tread edge E. Has a row of blocks lined up in the tire circumferential direction. In the present invention, if the shoulder block 6 is provided, other portions of the tread surface 2 can be arbitrarily formed. In this example, the central block 5 is provided between the vertical main grooves 3a, 3a, and the inner block 5 is also provided. An example is one in which the rib-shaped portion 7 is formed between the vertical main groove 3a and the outer vertical main groove 3b.

In the present embodiment, the buttress surface 9 connected to the tread edge E of the shoulder block 6 is
As shown in FIG. 2, FIG. 3, FIG. 4A, and FIG. 4B, the buttress contour line 10 in the cylindrical cross section K of radius r centering on the tire axis CP is convex outward in the tire axial direction. A curved surface portion 11 which is an arc-shaped curve and which is formed by a curved surface of which the arc-shaped curve approaches a straight line as the radius r is reduced is provided inward from the tread edge E in the tire radial direction. It has. Also, as is clear from FIG.
The width of the tire that connects to the contour line 10 through a corner
The facing surface extends without having a curved surface portion.

As a result, the shoulder block 6 can reduce the rigidity of the tread edge E without significantly reducing its rigidity, and the camber thrust can be shifted to the plus side. Here, as shown in FIG. 5, the camber thrust (CT) is a force that is generated at the time of rolling the tire 1 at a camber angle θ and is in a direction perpendicular to the traveling direction. When it works, it is expressed as plus, and when it works in the direction opposite to the tilting direction, it is expressed as minus. In the case where the camber thrust has a positive value, for example, when the tread edge E collides with the slope of the rut, an axial force for climbing the slope acts on the tire, so that the rut can get on and off smoothly. Therefore, the wandering performance can be improved.

In order to improve the wandering performance more remarkably, the curved surface portion 11 forms the arc-shaped curve from an arc and reduces the radius r, for example.
It can be composed of a curved surface to be the arc of curvature radius gradually large accompanied to. In this case, the radius of curvature R of the arc-shaped curve at the tread edge E is 1.5 to 4.5 times the tire circumferential length L of the shoulder block 6 (shown in FIG. 2), and more preferably 2.0 to. A factor of 4.0 is particularly desirable in that an optimal arcuate curve corresponding to the shape of the shoulder block 6 can be obtained and the camber thrust can be efficiently increased. In addition, when the arc of the arc-shaped curve 11 is composed of a plurality of arcs, the average radius of curvature can be substantially determined.

Further, in the present invention, since the wandering performance can be improved by forming such a curved surface portion 11 on the buttress portion 9 of the shoulder block 6, for example, the tread edge E is formed into an edge-shaped square shoulder. Of course, it is also possible to suppress the tread contact width TW of the tread surface 2 to a large extent and to suppress abnormal wear. Further, for example, since it is not necessary to provide a sipe in the tire axial direction at the tread edge E, it is possible to effectively prevent the occurrence of rubber chipping and uneven wear of the shoulder block 6 starting from the sipe, which contributes to a longer tire life. sell.

Further, the shoulder block 6 may form the curved surface portion 11 in a height range ha of at least 60% of the block height H, preferably 80% or more, and more preferably 100% in the tire radial direction. desirable. When the range ha of the curved surface portion 11 is less than 60% of the block height H, the effect of moderately relaxing the rigidity of the shoulder block 6 on the tread edge E side to improve the wandering performance is relatively reduced. On the contrary, the effect of improving the wandering performance will reach the ceiling even if it is provided over 100%.

On the inner side of the curved surface portion 11 in the radial direction of the tire, a flat surface portion 12 in which the buttress contour line 10 is a straight line can be formed. That is, FIGS. 4A to 4C respectively show the buttress contour lines 10 when the radius r of the cylindrical cross section K is sequentially reduced, but as shown in FIG. At 12, the buttress contour line 10 appears as a straight line. In such a heavy-duty tire, for example, as the tire wears, the tread edge E of the shoulder block 6 can be gradually changed from an arc-shaped curve to a linear shape. Therefore, for example, the edge effect of the tread edge E is enhanced, It is particularly preferable as an all-season heavy-duty tire that travels on icy and snowy roads.

FIG. 6 illustrates another embodiment of the present invention. In this example, the shoulder block 6 forms the curved surface portion 11 on the tread edge E via a narrow inclined surface portion 15 that extends inward in the tire radial direction toward the tire axial outer side. . That is, FIGS.
Similar to the example shown in, the tire near the tread edge E
The vertical main grooves 3b, 3b extending continuously in the circumferential direction and the vertical main grooves
A lateral groove 4d continuous between the groove 3b and the tread edge E
And a shoulder block partitioned by the tread edge E.
Inflator with block 6 forming a row of blocks lined up in the tire circumferential direction
Tires, the shoulder block 6
The buttress surface 9 connected to the end edge E is an outer side in the tire axial direction.
A small width that inclines inward in the tire radial direction
The curved surface portion 11 is formed via the inclined surface portion 15, and
The curved surface portion 11 is a cylindrical section with a radius r centered on the tire axis.
The buttress contour line 10 on the surface K is outside the axial direction of the tire.
Form an arc-shaped curve that is convex toward the side, and
As the radius r is reduced, the radius of curvature of the arc-shaped curve becomes larger.
It consists of a curved surface that approaches a straight line. Such an inclined surface portion 1
In No. 5, the camber thrust for climbing a slope such as a rut is made larger to further enhance the effect of improving the wandering performance. Maximum width Wa of the inclined surface portion 15 in the tire axial direction
Is preferably, for example, 5 to 15% of the maximum width of the shoulder block 6 in the tire axial direction. Further, the inclination angle θ1 of the inclined surface portion on the small angle side with respect to the tire circumferential direction is preferably, for example, 30 to 60 °.

FIG. 7 illustrates still another embodiment of the present invention. In this example, the shoulder block 6 shown in FIG. 6 is formed with a chamfered portion 16 formed of a substantially triangular slope in which both end edges of the shoulder block 6 in the tire circumferential direction are cut out in a chamfered shape. A thin groove 17 extending across the chamfer 16 is shown.

The narrow groove 17 has a groove width Wb of, for example, 1.5.
.About.3.0 mm, about 2.0 mm in this example, and a groove depth smaller than the groove width is illustrated. Also, this narrow groove 17
Is an arcuate curved portion 1 which is convex outward in the tire axial direction.
7A and end portions 17B and 17B that extend from both ends in the circumferential direction of the curved portion 17A to the lateral groove (fourth lateral groove 4d) and extend in a substantially linear shape in the tire circumferential direction are illustrated. In the shoulder block 6 of this embodiment, the rigidity of the shoulder block 6 is further optimized by the inclined surface portion 15, the chamfered portion 16, and the narrow groove 17, and the wandering performance can be improved.

Further, in the present embodiment, the fourth lateral groove 4d that crosses between the shoulder blocks 6 is formed as shown in FIG.
A groove bottom protrusion 19 is provided which protrudes from the groove bottom and connects between the shoulder blocks 6 adjacent to each other in the tire circumferential direction. The groove bottom raised portion 19 is continuous from the outside vertical main groove 3b side in the length direction of the fourth horizontal groove 4d at substantially the same height.
9a and an inclined portion 19b which is continuous with the terminal end X of the main portion 19a and whose height gradually decreases toward the tread edge E side.

The groove bottom ridge 19 is useful for increasing the rigidity in the tire circumferential direction such as suppressing a large collapse of the shoulder block 6 in the tire circumferential direction, and is provided on the road surface first-arrival side and rear-limb side of the shoulder block 6. Uneven wear can be suppressed. Further, since the groove bottom raised portion 19 includes the inclined portion 19b, the rigidity of the shoulder block 6 optimized by the curved surface portion 11 is not impaired, and it is also useful for improving the wandering performance.

As described above in detail, in the present invention, the category of tires is not limited to the above-mentioned examples.
It can be used for pneumatic tires of various categories such as for light trucks. Further, it is desirable to form the buttress surface 9 including the curved surface portion 11 on all the shoulder blocks 6 of the tire.
If it is provided in 70% or more of the total number, the wandering performance can be improved.

[0028]

EXAMPLES Next, examples in which the present invention is embodied will be described. The tire size having the structure shown in FIG. 1 and having the shoulder block 6 according to FIG. 2 is 11R22.5.
A 14P heavy-duty radial tire was prototyped according to the specifications in Table 1, and the camber thrust and wear performance of each sample tire were tested. The curved surface portion has a buttress contour line at the tread edge as an arc with a radius of curvature of 110 mm,
And at the groove bottom position of the lateral groove the buttress contour line is a straight line,
Between these, the buttress contour edge is formed of a curved surface with a smoothly varying radius of curvature.

The camber thrust is a rim (22.5 × 7.50) used, an internal pressure (700 kPa), a load (26.72 kN), and the value when the camber angle θ is 2 degrees is measured by a tire cornering tester. It was measured using. In addition, the wear performance is 20-ton 2-D
The wear appearance of the shoulder block after the vehicle was mounted on the front wheels of the constant loading vehicle of No. 4 and traveled 20000 km was visually inspected.

As an object for comparing the effects of the present invention,
The tire of Comparative Example 1 in which the buttress contour edge is a straight line over the entire buttress surface of the shoulder block, and the tire of Comparative Example 2 in which sipes are arranged in the tire circumferential direction at the tread edge of the shoulder block of the tire of Comparative Example 1 ( Figure 8
(C) type) was also tested. The test results are shown in Table 1.

[0031]

[Table 1]

As a result of the test, in the tires of Examples and Comparative Example 2, the camber thrust is largely shifted to the plus side as compared with the tire of Comparative Example 1, and it can be confirmed that the wandering performance is improved. However, in the tire of Comparative Example 2, track wear occurred on the tread edge of the shoulder block, but it was confirmed that the tires of the Examples were worn evenly. Thus, it was confirmed that the pneumatic tire of the present invention has improved wandering performance without impairing wear performance.

[0033]

As described above, the pneumatic tire of the present invention can effectively improve the wandering performance without causing uneven wear, lack of rubber, or a large reduction in the ground contact width.

[Brief description of drawings]

FIG. 1 is a development view of a tread surface showing an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing the shoulder block.

FIG. 3 is a diagram illustrating a cylindrical cross section.

4A to 4C are cylindrical cross-sectional views of shoulder blocks in which the radius r of the buttress surface is different.

FIG. 5 is a diagram illustrating camber thrust.

FIG. 6 is a perspective view of a shoulder block showing another embodiment of the present invention.

FIG. 7 is a perspective view of a shoulder block showing still another embodiment of the present invention.

8A to 8C are diagrams for explaining a conventional technique.

[Explanation of symbols]

2 tread surface 3 vertical main groove 4 lateral grooves 6 shoulder block 9 Buttress surface 10 Buttress contour 11 arc-shaped curve 12 Plane 15 Inclined surface part 16 chamfer 17 narrow groove E tread edge K cylindrical cross section

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Claims (3)

(57) [Claims] 1. A vertical main groove extending continuously in the tire circumferential direction near the tread edge, a lateral groove continuous between the vertical main groove and the tread edge, and the tread edge. In the pneumatic tire in which the shoulder blocks form a row of blocks arranged in the tire circumferential direction, the buttress surface continuous with the tread edge of the shoulder block has a buttress contour line in a cylindrical cross section with a radius r around the tire axis, The curved surface portion has a curved surface that is convex toward the outside in the tire axial direction, and has a curved surface portion that is a curved surface that increases in radius of curvature of the curved curved surface and approaches a straight line as the radius r is reduced. The surface portion is characterized in that the radius of curvature of the arc-shaped curve at the tread edge is 1.5 to 4.5 times the tire circumferential length L of the shoulder block. Tire Ri. 2. The buttress surface includes the curved surface portion in an area radially inward of the tire from the tread edge, and the flat surface portion in which the buttress contour line is straight inside the curved surface portion in the tire radial direction. The pneumatic tire according to claim 1 , further comprising: 3. A tire circumferential direction is continuous in the vicinity of the tread edge.
The vertical main groove that extends and the vertical main groove and the tread edge
It is divided by a lateral groove continuous between the above and the tread edge.
The shoulder blocks form a row of blocks lined up in the tire circumferential direction.
A pneumatic tire made of a bat that is continuous with the tread edge of the shoulder block.
The bearing surface is in the tire radial direction outward in the tire axial direction.
Curved surface part through a small inclined surface part that inclines and extends inward
And the curved surface portion is a circle with a radius r centered on the tire axis.
The buttress contour line in the cylinder cross section is outside in the tire axial direction
Has an arc-shaped curve that is convex toward
As r is reduced, the radius of curvature of the arc-shaped curve becomes large.
A pneumatic tire characterized by a curved surface that approaches a straight line .